1. Field of the Invention
The present invention relates to a conveyance method and apparatus for a processing step, used in a conveyance line in which processing is carried out, such as a coating line or a machining line, or the like, in a manufacturing plant.
2. Description of the Related Art
A prior art example of a conveyance apparatus whereby a vehicle body is coated whilst being conveyed is disclosed in International Patent WO 02/053482. This conveyance apparatus is provided with a conveyance truck that is able to travel over immersion tanks, and pairs of swinging arms are provided on the conveyance truck, as two sets, at the front section and at the rear section in the direction of travel. Supporting bars are installed respectively between the free end sections of the pairs of swinging arms, and a vehicle body is supported on top of the front side supporting bar and the rear side supporting bar. By causing the front and rear side swinging arms to rotate downwards, in either an independent fashion or a mutually combined fashion, the vehicle body held on the supporting bars is caused to descend and is immersed in a treatment liquid.
However, in the prior art described above, since the vehicle body is raised and lowered along an arc-shaped path of descent, then it is necessary to form the entrance to the immersion tank and the exit from same, to a large dimension in the direction of travel of the conveyance truck. Moreover, if the vehicle body is to be lowered in a perpendicular vertical direction, then it is necessary to move the conveyance truck in the direction of travel. Furthermore, if the direction of descent and ascent is an arc-shaped direction, then a problem arises in that the positional control of the vehicle body, and the control of the angular position of the vehicle body with respect to its angular position when immersed in the treatment liquid and its angular position when removed from same, become complicated.
Therefore, it is an object of the present invention to provide a conveyance method and apparatus for use in processing stages, whereby the positional control of the conveyed object is simplified, and the raising and lowering operations for carrying out processing can be executed by means of simple controls, by causing the conveyed object to be raised and lowered along a movement path that is more proximate to a perpendicular vertical path.